UNCONSOLIDATED INVESTMENTS - Income from Unconsolidated Investments (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) property	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Equity Method Investments and Joint Ventures [Abstract]
Equity in joint venture income	$ 70.5	$ 58.2	$ 45.4
Equity in joint venture income (loss) - fair value	56.6	34.9	(0.7)
Interest income recognized	(0.5)	4.3	9.5
Total interest income and foreign currency gain (loss)	126.6	97.4	54.2
Schedule of Equity Method Investments [Line Items]
Gain on sale of real estate	$ 130.7	$ 72.4	$ 0.0
Equity method investment, ownership percentage			25.00%
Equity method investment, realized gain (loss) on disposal			$ 26.6
Multifamily [Member]
Schedule of Equity Method Investments [Line Items]
Number of real estate properties sold | property	5
Gain on sale of real estate	$ 59.0